Duplex counterweightless shuttle elevator system

ABSTRACT

Elevator cars suspended from opposite ends of a traction driven hoist cable counterbalance each other and provide ideal spacing between cars serving two terminal floors such as a main floor and a sky lobby. A leveling device on one or both cars provides for adjustment of the position of the associated car relative to the hoist cable to accommodate for cable stretch and settling of the building so that each car can be brought into exact registry with the adjacent landing. The cars can be arranged to stop at pairs of intermediate floors located equal distances from the two terminal floors and can be further arranged to distribute load in opposite directions from a third terminal located halfway between the first and second terminals. The counterbalanced cars can be combined with a second elevator system, either a conventional system or a counterbalanced system, for sky lobby operation with the counterbalanced car system providing either the shuttle service, the local service or both.

United States Patent 1 Berkovitz [45] Aug. 7, 1973 DUPLEXCOUNTERWEIGHTLESS SHUTTLE Primary Examiner-Richard E. Aegerter ELEVATORSYSTEM Assistant Examiner-Merle F. Maffei [75] Inventor: HarryBerkovitz, Glenrock, NJ. l li i ifi [5 7] ABSTRACT [73 Asslgnee: y g sElectric Corporation. Elevator cars suspended from opposite ends of atracmsburg tion driven hoist cable counterbalance each other and [22]Filed; 29 1971 provide ideal spacing between cars serving two terminalfloors such as a main floor and a sky lobby. A level- PP Nod 213,587 ingdevice on one or both cars provides for adjustment Related U.S.Application Data Division of Ser. No. 30,375, April 21, 1970, Pat. No.

| MAIN LANQING Field of Search 187/16, 20, 94;

of the position of the associated car relative to the hoist cable toaccommodate for cable stretch and settling of the building so that eachcar can be brought into exact registry with the adjacent landing. Thecars can be arranged to stop at pairs of intermediate floors locatedequal distances from the two terminal floors and can be further arrangedto distribute load in opposite directions from a third terminal locatedhalfway between the first and second terminals. The counterbalanced carscan be combined with a second elevator system, either a conventionalsystem or a counterbalanced system, for sky lobby operation with thecounterbalanced car system providing either the shuttle service, thelocal service or both.

r I MAIN LANDING P Amguws mu SHEEI 1 BF 2 UPPER TERMINAL 3 a m I #1 l I.d W UJI m w J l- L u I LOWER TERMINAL I UN a; QC FIGJ.

PAIENIEBAUG mm SHEEP? Bf 2 a MMN LANDING DUPLEX COUNTERWEIGHTLESSSHUTTLE ELEVATOR SYSTEM CROSS REFERENCE TO RELATED APPLICATION Thisapplication is a division of application Ser. No. 30,375, filed Apr. 2],1970, now U.S. Pat. No. 3,651,893 which is assigned to the same assigneeas the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to elevator systems and more particularly to traction drivenelevator systems. 2. Prior Art The traction drive has been used in theelevator field for many years. According to this system, the car issupported by a hoist cable which passes over a sheave hav-- ing aU-shaped groove in its periphery. The car is counterbalanced by acounterweight connected to the other end of the hoist cable. The weightof the car plus its load acting on one end of the hoist cable and theweight of the counterweight acting on the other end, apply a force tothe hoist cable which is translated into a traction force between thecable and the sheave. Therefore, when a rotational force is applied tothe sheave, the car is caused to move up and down in a hoistway. Sincethe counterweight is conventionally made equal to the weight of theempty car plus 40 percent of the load capacity of the car, this systemhas the advantage that only enough torque sufficient to drive thedifference in loadneed be provided. In addition, the system has aninherent safety feature in that when the car over travels in the updirection the counterweight will strike the bottom of the hoistway sothat the traction force is lost and the sheave can slip before the caris drawn into the machinery. The disadvantage of the system is the extraapparatus required. The counterweight like the car needs a guide railsystem in addition to a buffer and takes up space in the hoistway. Ofcourse, a separate drive motor is required for each elevator car.

Various schemes have been proposed for developing more efficientelevator systems. The combination for use in high-rise buildings of ashuttle system to transport passengers from the main lobby directly toupper lobbies from which they are transported to the desired floor by alocal elevator system, was disclosed in U.S. Pat. No. 1,967,832.Apparatus useful in coordinating the movement of the shuttle cars andthe local cars was disclosed in U.S. Pat. No. 3,467,223.

Other approaches to increasing the efficiency of elevator systemsincludes the operation of two cars in the same hoistway. U.S. Pat. No.1,837,463 discloses such a system wherein the two independently operatedcars share a common counterweight whereas in the system disclosed inU.S. Pat. No. 1,911,834 a separate counterweight is provided for eachcar. Still another approach has been the utilization of double-deckerand even triple-decker cars such as those shown in U.S. Pat. Nos.1,693,651, 1,997,260 and 1,199,174. One difficulty with the multiplecabin cars is achieving accurate registry of each cabin with theadjacent landing. U.S. Pat. No. 1,199,175 discloses a system whereinalthough both cabins move in a common sling and share a commoncounterweight they are driven by separate motors through separatecabling systems so that the cars can be independently leveled. U.S. Pat.No. 1,490,271 has suggested that inaccuracies in leveling a singlefreight car could be compensated for by tilting a section of theflooring of the elevator or the building to facilitate the loading andunloading of wheeled vehicles.

In order to provide elevator service in the upper portion of the EiffelTower, an elevator system was developed wherein one car which is drivenby a direct acting hydraulic ram operates between the top of the towerand a mid-station. A second car suspended from a cable connected to thefirst car operates in a parallel shaft between the midpoint and a lowerterminal. Passengers transfer between cars at the mid-station in orderto go all the way to the top. This system is de scribed in the 1969annual issue of Elevator World, Volume XVII, No. 10 dated October, 1969chapter 3.

SUMMARY OF THE INVENTION According to this invention two elevator carssuspended from opposite ends of a hoist cable driven by a tractionsheave act as counterweights for each other thereby eliminating the needfor separate counterweights and their associated equipment. In thismanner, a single machine only slightly larger than each of the machinesrequired to drive two elevator cars in the conventional arrangement issufficient to supply the torque required for the maximum out of balancecondition that will be encountered. The elimination of separatecounterweights reduces the cross-sectional hoistway area required foreach car on. the order of 15 percent thereby freeing more space in thebuilding for other purposes.

Another feature of the invention is the leveling means which permitsadjustment of the position of one or both cars relative to the hoistcable to compensate for cable stretch caused by variations in theloading of the cars so that both cars may be brought into exact registrywith the adjacent landing simultaneously. In the exemplary embodiment ofthe invention disclosed, this adjustment is achieved through utilizationof a rectangular array of four interconnected jacks which vary thevertical position of the associated car relative to the car sling.

The counterbalancing cars can be operated reciprocally between twoterminals. This arrangement is particularly useful for shuttle servicebetween a lower terminal and a sky lobby in a high-rise building. Thereciprocal action of the cars provides ideal separation between the carsfor this type of service. The system can be arranged for serving pairsof floors located between the terminal floors with one floor in eachpair located the same distance from one terminal that the other landingin the same pair is from the other terminal. The cars can also bearranged to simultaneously serve an intermediate landing located halfwaybetween the two terminals. When additional landings located equaldistances above and below said intermediate landing are provided, thesystem can be utilized to distribute load simultaneously above and belowthe intermediate landmg.

The counterbalancing cars can be combined with a second elevator systemto provide shuttle and local service in a high-rise building. Forinstance, the counterbalancing cars can serve as shuttle cars to deliverload to one or more sky lobbies from which other elevator systemsprovide local service. When used for the local lobby located at theabove-mentioned intermediate landing of the local elevator rise.

In order to minimize hoistway space when the cars operate in oppositedirections from an intermediate landing, the hoistway for the carserving the upper landing need only extend from the intermediate landingto the drive sheave, while the hoistway for the car serving the floorsbelow the intermediate landing need only extend from slightly above theintermediate landing to the lowest floor. The portion of the hoist cablesupporting the lower car can be routed down the hoistway for the uppercar and then aligned with the lower hoistway by deflecting sheaveslocated slightly above the intermediate terminal. Alternatively, the twocars can be operated in the upper and lower portions of a commonhoistway by similar deflecting sheaves.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention, refernce may be had to the preferred embodiments, exemplaryof the invention, shown in the accompanying drawings in which:

FIG. 1 is a schematic view in elevation of an elevator system embodyingthe invention;

FIG. 2 is an isometric view of an elevator car illustrating details ofan exemplary embodiment of the invention; and

FIG. 3 is a schematic view of exemplary arrangements of elevator systemsaccording to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, elevatorcars l and 3 are suspended from opposite ends of a hoist cable 5. Thehoist cable 5 is reeved over traction sheave means 7 including a drivesheave 9 and a secondary sheave l l. A hoist rope 5 rides in U-shapedgrooves in the periphery of the sheaves 9 and 11. The weight of the carsacting on opposite ends of the hoist cable provides the traction forcebetween the cable and the U-shaped grooves which permits the cars to beraised and lowered when the drive sheave 9 is rotated by the shaft 13connected to the elevator machine 15. This type of traction drive is incommon use in conventional elevator systems wherein the elevator car isconnected to one end of the hoist cable and a counterweight is connectedto the opposite end.

The secondary sheave ll permits another wrap around the drive sheave 9to increase the traction and also permits horizontal separation betweenthe ends of the hoist cable 5 so that the elevator cars l and 3 can besuspended in the hoistway l7 slde-by-side without interference. As isthe general practice in the elevator field, cars l and 3 are guided intheir vertical travel through the hoistway by guide shoes 19 which rideon guide rails 21 mounted to the walls of the hoistway.

As is common practice in high-rise elevator systems, a compensation rope23 connected to the bottom of each car accommodates for variations insuspended load imposed on either end of the hoist cable 5. For instance,as shown in FIG. 1 with the elevator car 1 located adjacent a lowerterminal and the elevator car 3 located adjacent an upper terminal, mostof the weight of the hoist cable 5 is imposed on the side of the drivesystem supporting the elevator car 1. As the elevator car 1 travels upin the hoistway and the elevator car 3 travels downward this load due tothe weight of the hoist cable 5 shifts from the elevator car 1 to theelevator car 3 thereby causing variations in torque requirements. Withthe compensation rope 23 similar in unit weight to the hoist cable 5,the combined weight due to the hoist cable and the compensation ropeimposed on either side of the drive system remains constant. As isusual, a compensator 25 located at the bottom of the hoistway guides thecompensation rope and prevents it from lashing about. Although the hoistcable 5 and the compensation rope 23 are shown as single strands for thesake of simplicity, it is to be understood that they may be composed ofmultiple steel ropes as is conventional in heavy duty elevator systems.Control cables 27 and 29 connect cars l and 3, respectively with theelevator supervisory control (not shown).

It is evident from FIG. 1 that as the machine 15 is energized, the drivesheave 9 is rotated thereby causing the elevator cars l and 3 toreciprocate in the hoistway 17. It is also clear from FIG. 1 that whenthe elevator car 1 is at the lower terminal the elevator car 3 is at theupper terminal, and as shown in the dotted lines, when the elevator car1 is at the upper terminal the elevator car 3 is adjacent the lowerterminal. This arrangement, therefore, inherently provides ideal spacingbetween the two cars operating between the lower and upper terminals.

If one of the elevator cars such as the elevator car 3 is replaced by acounterweight, the system disclosed in FIG. 1 is similar to theconventional elevator system now widely in use. According to thisinvention, however, the conventional dead load counterweight is replacedby another elevator car which can do useful work. This is especiallysignificant in high-rise installations where the ratio of the useful payload to the total suspended load becomes less and less as the weight ofthe hoist cable and compensation ropes increases.

When viewed from another perspective, the invention contemplates a twocar installation with a substantial reduction in the amount of machineryrequired. For instance, the two counterweights and their associatedguide rail systems are eliminated completely. In addition, only onehoist cable, one compensation rope, one compensator, one traction sheavedevice, one elevator machine and one controller is required therebyeliminating duplicates of each of these items as required in theconventional two car system. Since it is the usual practice to make thecounterweight equal to the weight of the car plus 40 percent of the loadcapacity of the car, the machine used in the duplex system will have tobe slightly larger to supply sufficicnt torque for the percent load outof balance condition. However, it is estimated that only about 10percent more torque would be required and less additional torque wouldbe required the higher the rise since in those installations the payload is a proportionally smaller percentage of the suspended load.Through the elimination of much of the apparatus, the duplex systemgreatly reduces the load that must be supported by the building for twocar elevator service. In addition, the elimination of the counterweightsand their guide rail systems reduces the hoistway cross-sectional arearequired for each car by approximately 15 percent, which means that morespace is available for rental or other purposes.

With the higher rise elevators, hoist cable stretch becomes asignificant problem. Cable stretch has two components, structuralstretch which is the permanent stretch experienced by a new cable andelastic stretch which is a temporary stretch and is a function of theload imposed on the cable. Great strides have been taken to reducestructural stretch. Rope suppliers are now providing prestressed ropefor a nominal charge and approximately one half the structural stretchcan be eliminated by going to independent wire rope center ropes. Thestructural stretch, which is initially the largest component, can betaken care of by adjustable hitches on one or both cars.

The amount of elastic stretch is a continuously varying factor. It notonly depends upon the load in the car, but also the length of the cableon which that load is acting. For instance, if the elevator car I is inexact registry with the lower terminal and then the car becomes fullyloaded, the car will sink lower below the level of the lower terminalthan it would if it became fully loaded when adjacent the upperterminal. in highrise buildings this elastic stretch can reach as muchas 2 to 3 inches causing a serious tripping hazard for passen' gersentering and leaving the car. In the conventional elevator system thecar is merely releveled by slow speed operation of the hoist motor. Thisof course also repositions the counterweight. However, since theposition of the counterweight is not critical this method of relevelingis entirely satisfactory in those systems.

It is obvious, however, in the system disclosed in FIG. 1 that if theelevator car 1 is in exact registry with the lower terminal and theelevator car 3 is in exact registry with the upper terminal and then theelevator car 1 becomes fully loaded thereby causing it to sink 2 inchesbelow the level of the lower terminal due to elastic stretch, operatingthe hoist motor to bring the elevator car 1 up to the level of the lowerterminal will cause the elevator car 3 to be displaced below the levelof the upper terminal thereby causing a tripping hazard for passengersentering and leaving elevator car 3.

in order to overcome this difficulty it is contemplated by thisinvention that at least one of the elevator cars be provided with atleast a limited amount of movement with respect to the hoist cable 5.For instance, in the example just discussed if the elevator car 3 ismovable with respect to the hoist cable 5, then when the hoist motor 15is operated to relevel the elevator car 1 the adjusting means can beoperated to move the elevator car 3 up with respect to the hoist cable 5thereby maintaining it level with the upper terminal. If on the otherhand, it is the car equipped with the adjusting means which must bereleveled due to a change in the loading of the ear, the hoist motorwould not be activated since the adjusting means would make theadjustment necessary. Alternatively, both cars could be provided withthe adjusting means and could be independently operated withoutaffecting the other car.

An exemplary means for providingadjustment between the positioning ofthe elevator car and the hoist cable is shown in FIG. 2 wherein the caris supported by a sling identified by the general reference character33. The sling is composed of two lower horizontal channel members knownas safety channels 35 and 37, two vertical members known as stiles 39and 41 and two upper channel members 43 and 45. The sling forms avertical rectangular frame which surrounds the cab 31. The sling isconnected to the hoist cable 5 (shown in FIG. 2 as being composed of sixseparate wire ropes) through a hitch (not shown) on a plate 47 fastenedto the upper horizontal channel members 43 and 45.

The guide shoes 19 mentionedeariler which cooperate with the guide railsin the hoistway to guide the car in its upward and downward travel areconnected to the stiles near their upper and lower extremities. Twohorizontal angle members 49 and 51 are connected to the safety channels35 and 37 near the stiles. A cross member 53 is supported by thehorizontal arms of the angles 49 and 51. Four Duff-Norton worm gearjacks 55 are arranged in a rectangular array near the extremities of theangle members 49 and 51. All four jacks are driven by a motor andcontroller 57 mounted on the cross member 53 through a reducer 59 :andconnecting shafts 61. The cab 31 is supported by the four jacks throughappropriate resilient mountings (not shown). Operation of the motor 57causes the cab 31 to be raised and lowered relative to the sling, andtherefore the hoist cable 5, in a level attitude through the coordinatedoperation of the jacks 55. Since it is desirable that the adjustingspeed be on the order of 2 feet per minute, the power requirements forthe motor 57 would be less than 1 horse power.

Guide shoes 63 cooperate with flanges on the inside of the stiles 39 and41 to guide the upper portion of the cab while adjustments are beingmade. The entire cab 31 including the door operator 67 which operatesthe car door through the well known linkage 69 is moved by the adjustingmeans. The auxiliary equipment 71, such as the inductor relays whichcooperate with apparatus in the hoistway to determine the position ofthe car relative to the landing, etc., is also mounted on the cab 31 andis therefore raised and lowered by the adjusting means. It is obviousthat the means for adjusting the position of the cab with respect to thehoist cable 5 could take many other forms.

In addition to accommodating for cable stretch, the adjusting mechanismis also useful in correcting for the settling of the building in whichthe elevator is installed. Of course, where the duplex elevator onlyoperates between an upper and a lower terminal, the adjustment forsettling of the building could be taken up by the hitch. However, wherethe duplex system serves a number of intermediate landings theadjustment means provide ideal accommodation for the variations in thesettling of the building at the different landings.

The duplex elevator system can be arranged in a number of configurationsto provide a wide variety of elevator service. FIG. 3 illustrates anumber of exemplary arrangements. This Figure is not intended toillustrate a specific arrangement for a particular building but rathershows in composite form a variety of arrangements for the duplex system.

I FIG. 3 illustrates a 36 story building having a main landing serving35 landings numbered consecutively from the landing just above the mainlanding. The sky lobbies SLA, SLR and SLC are provided at the tenth,twentieth and thirtieth floors respectively. The sky lobbies aretransfer floors at which passengers transfer from express or shuttlecars from the main landing to local cars for the floor desired. The skylobby SLA is served by shuttle system SS1 comprising thecounterbalancing duplex cars 81A and 81B. These two cars reciprocatebetween the main landing; and sky lobby SLA in a manner which will beclear from the previous diseussion.

Sky lobby SLB is served by shuttle system SS2 comprising thecounterbalancing cars 512A and $28 which reciprocate between mainlanding and the sky lobby SLB again in a manner which will be evidentfrom the above discussion. in addition, since the sky lobby SLA islocated mid-way between the main landing and SLB, the cars 52A and 828may be stopped at SLA simultaneously. in this manner, the shuttle systemSS2 may be utilized to serve both SLA and SLB if desired.

The sky lobby SLC is served by the shuttle system SS3 as the cars SSAand SSH reciprocate between the main landing and SLC. Since the skylobby SLA is the same distance above the main landing that the sky loobySLB is below SLC, the car S3A will be adjacent the sky lobly SLA whenthe car 838 is adjacent the sky lobby SLB and vice versa. It is evidentthen that the shuttle system SS3 may be utilized to serve just the skylobby SLC or all of the sky lobbies. Of course with the combinaion ofshuttle systems illustrated in FIG. 3, during peak hours the shuttlesystem SS1 can be arranged to serve the sky lobby SLA, while the systemSS2 serves only the sky lobby SLR and the system SS3 serves only the skylobby SLC. During light traffic hours the systems S81 and SS2 could beshut down and the system SS3 could serve all of the sky lobbies.

The shuttle elevator systems which provide service between the mainlanding and the sky lobbies can be combined with second elevator servicefor providing local service to the floors adjacent the sky lobbies. Thelocal elevator cars can be either the duplex counterbalancing cars orconventional counterweighted cars. Conventional counterweighted cars canbe arranged in many ways to provide local service from a sky lobby. Forinstance, all of the local service cars can be arranged to serve all ofthe floors between the sky lobby being served and the next higher skylobby. Alternatively a single car or a group of cars can be arranged toserve certain of the floors between the sky lobby being served and thenext higher sky lobby and a second car or second group of cars can bearranged to serve another group of floors between the sky lobby beingserved and the next higher sky lobby. Such a system is shown in FIG. 3where the conventional counterweighted elevator system Ll serves the skylobby SLR and floors 21 through 24 while the local car L2 serves the skylobby SLB and floors 25 through 29.

In yet another arrangement, the local cars can be arranged to servefloors above and below the associated sky lobby. For instance, in FIG. 3the elevator system Ll serves the floors halfway between sky lobbies SLBand SLC while the elevator system L3 serves the floors halfway betweensky lobby SLB and sky lobby SLA. Of course in practice the local bank ofelevators would be located closer to the shuttle system serving thecommon sky lobby.

As mentioned above, the second elevator system providing local servicecan also take the form of the duplex counterbalancing system describedin detail above. For instance, the local system such as L4 comprisingthe counterbalancing cars L4A and L4H can be arranged to provide localservice above and below the sky lobby SLA. With both of the carssimultaneously adjacent sky lobby SLA, one car can be loaded withpassengers desiring service to floors ll through while the other car issimultaneously loaded with passengers desiring service to floors fivethrough nine. With the landings nine and l l, eight and 12, seven and13, six and i4, and five and 15 being equal distances below and abovesky lobby SLA, respectively, when one of the cars of system L4 isadjacent one of the landings in each pair the other car is adjacent theother landing so that both of the cars may be transferring passengers tothe local floors simultaneously.

As arranged in FIG. 3, the cars L4A and L4B can each serve all of floorsfive through 15. This duplication of effort is not necessary, however,and the car may be alternatively arranged so that one car serves onlythe landings above the associated sky lobby while the other car servesonly the landings below the associated sky lobby. For instance, in thesystem L5 shown in FIG. 3 the car L5A can only serve sky lobby SLB andfloors 21 through 24 since the hoistway for that car does not extendbelow the sky lobby SLB. On the other hand, the car LSB can only servethe sky lobby SLB and floors 16 through 19 since its hoistway does notextend to the 24th floor. The end of the hoist cable supporting the carLSB is routed down the side of the hoistway for the car LSA and then isaligned with the center of the hoistway for the car L5B by deflectionsheaves 73. Of course, the hoistway for the car LSB must extend slightlyabove the sky lobby SLB to provide room for the deflecting sheaves. Thenet result is that the hoistway spaced required is reduced to a minimum.Remembering that with the duplex system the cross-sectional area of eachhoistway is reduced by approximately 15 percent due to the eliminationof the counterweight, this arrangement releases the maximum amount ofspace for other useful purposes.

Another local duplex system L6 similar to the system L5 but serving thesky lobby SLC illustrates how the local systems can be combined toprovide service to all the floors between sky lobbies.

The local system L7 shows yet another possible arrangement for theduplex counterbalancing cars. in this system the car L7A serves skylobby SLC and floors 25 through 29 while the car L7B serves sky lobbySLB and floors 2l through 25. In this arrangement the cars can load andunload at their associated sky lobbies simultaneously. it should also beobserved that according to this arrangement if the sky lobbies were anodd number of floors apart, the cars would not have to duplicate serviceto the common intermediate floor.

The system L8 shows yet another exemplary arrangement of the duplexcounterbalancing cars. In this system the cars operate in a commonhoistway with the car LSA serving the sky lobby SLA and floors sixthrough nine while the car L8B serves the main landing and landings onethrough four. Of course according to this arrangement neither car canserve the fifth floor since that space is occupied by the deflectionsheaves 73, however, this space could be occupied by a service floorcontaining heating and air conditioning equipment as is common in modernbuildings.

As mentioned above the specific arrangements illustrated are meant to beillustrative only since it is obvious that an infinite variety ofarrangements could be conceived within the scope of the invention. Forinstance, the system L4 or L5 which operates from a certainly locatedlobby could be adapted for use in unconventional buildings such as thosebuilt on a hillside where the main landing is located at the center ofthe structure.

I claim as my invention:

1. in an elevator system a structure having first and second landingsvertically displaced along a hoistway, two elevator cars, tractionsheave means mounted at the top of the hoistway, a hoist cable reevedover said traction sheave means, said elevator cars being suspended fromopposite ends of said hoist cable in counterbalancing relation so thatwhen one car is adjacent one landing the other car is adjacent the otherlanding, drive means connected to said traction sheave means andoperative to raise and lower the counterbalancing cars in opposition toeach other to serve the landings, third and fourth landings locatedbetween said first and second landings with said third landing being thesame distance from said first landing as the fourth landing is from saidsecond landing, and deflecting sheave means located between said thirdand fourth landings for deflecting one side of said hoist cable so thatthe car suspended from said one side of said hoist cable recoprocates insaid hoistway directly below the other car, whereby the two cars operatealong a common vertical axis with said one car being adjacent the firstlanding when said other car is adjacent the second landing and said onecar is adjacent the third landing when said other car is adjacent thefourth landing.

2. In an elevator system a structure having first, second, and thirdlandings vertically displaced in ascending order, first and secondelevator cars, first and second hoistways for said first and secondelevator cars, respectively, traction sheave means mounted at the top ofthe first hoistway, a hoist cable reeved over said traction sheavemeans, said elevator cars being suspended from opposite ends of saidhoist cable in counterbalancing relation so that when one car isadjacent the first landing the other car is adjacent the third landing,drive means connected to said traction sheave means and operative toraise and lower the counterbalancing cars in opposition to each other toserve the landings, said first hoistway extending from said thirdlanding to said second landing with said second hoistway being parallelto and adjacent said first hoistway and extending from substantiallysaid second landing to said first landing, the side of said hoist cablesupporting said first car being routed down said first hoistway, andincluding deflection sheave means above said second landing for guidingsaid hoist cable so that said second car is suspended in said secondhoistway, whereby said first car operates between said second, and thirdlandings while said second car operates between said second and firstlandings.

3. The system of claim 2 including additional pairs of landings with onelanding of each pair being located in said first hoistway substantiallythe same distance above said second landing as the other landing in thesame pair is located below said second landing in the second hoistway,whereby when the first car is adjacent one landing in each pair thesecond car is substantially adjacent the other landing in that same pairof landings.

4. The elevator system of claim .3 including adjusting means associatedwith at least a first one of the elevator cars and operative to adjustthe position of said first car relative to the hoist cable whereby bothcars can be brought into exact registry with the adjacent landingsimultaneously despite stretch of the hoist cable caused by variationsin the loading of the cars and despite settling of the structure.

l 'k l

1. In an elevator system a structure having first and second landingsvertically displaced along a hoistway, two elevator cars, tractionsheave means mounted at the top of the hoistway, a hoist cable reevedover said traction sheave means, said elevator cars being suspended fromopposite ends of said hoist cable in counterbalancing relation so thatwhen one car is adjacent one landing the other car is adjacent the otherlanding, drive means connected to said traction sheave means andoperative to raise and lower the counterbalancing cars in opposition toeach other to serve the landings, third and fourth landings locatedbetween said first and second landings with said third landing being thesame distance from said first landing as the fourth landing is from saidsecond landing, and deflecting sheave means located between said thirdand fourth landings for deflecting one side of said hoist cable so thatthe car suspended from said one side of said hoist cable recoprocates insaid hoistway directly below the other car, whereby the two cars operatealong a common vertical axis with said one car being adjacent the firstlanding when said other car is adjacent the second landing and said onecar is adjacent the third landing when said other car is adjacent thefourth landing.
 2. In an elevator system a structure having first,second, and third landings vertically displaced in ascending order,first and second elevator cars, first and second hoistways for saidfirst and second elevator cars, respectively, traction sheave meansmounted at the top of the first hoistway, a hoist cable reeved over saidtraction sheave means, said elevator cars being suspended from oppositeends of said hoist cable in counterbalancing relation so that when onecar is adjacent the first landing the other car is adjacent the thirdlanding, drive means connected to said traction sheave means andoperative to raise and lower the counterbalancing cars in opposition toeach other to serve the landings, said first hoistway extending fromsaid third landing to said second landing with said second hoistwaybeing parallel to and adjacent said first hoistway and extending fromsubstantially said second landing to said first landing, the side ofsaid hoist cable supporting said first car being routed down said firsthoistway, and including deflection sheave means above said secondlanding for guiding said hoist cable so that said second car issuspended in said second hoistway, whereby said first car operatesbetween said second, and third landings while said second car operatesbetween said second and first landings.
 3. The system of claim 2including additional pairs of landings with one landing of each pairbeing located in said first hoistway substantially the same dIstanceabove said second landing as the other landing in the same pair islocated below said second landing in the second hoistway, whereby whenthe first car is adjacent one landing in each pair the second car issubstantially adjacent the other landing in that same pair of landings.4. The elevator system of claim 3 including adjusting means associatedwith at least a first one of the elevator cars and operative to adjustthe position of said first car relative to the hoist cable whereby bothcars can be brought into exact registry with the adjacent landingsimultaneously despite stretch of the hoist cable caused by variationsin the loading of the cars and despite settling of the structure.